Compensation-free broadband entangled photon pair sources

Area of Science:

• Quantum optics
• Quantum information science

Background:

• Broadband biphotons entangled in polarization and time-energy are crucial for quantum communication, sensing, and metrology.
• Generating high-quality entanglement over broad spectra traditionally requires complex compensation techniques to manage distinguishabilities.

Purpose of the Study:

• To demonstrate a compensation-free method for generating broadband polarization-entangled biphotons.
• To investigate the role of group birefringence and dispersion in spontaneous parametric down-conversion (SPDC) bandwidth and entanglement quality.

Main Methods:

• Utilizing type-II SPDC in nonlinear materials with low group birefringence.
• Employing periodically poled silica fiber (PPSF) as the nonlinear medium.
• Analyzing the interplay between group birefringence and dispersion effects.

Main Results:

• Identified low group birefringence as key to dispersion-limited biphoton bandwidth, eliminating the need for compensation.
• Achieved high polarization-entanglement concurrence (>0.977) over a broad spectral range (>77nm) using PPSF.
• Demonstrated a compensation-free source for broadband polarization-entangled photons.

Conclusions:

• Periodically poled silica fiber is an ideal medium for generating high-concurrence polarization-entangled biphotons without compensation.
• The developed method offers a simplified and effective approach to creating essential quantum resources.
• This work advances the generation of broadband entangled photons for various quantum applications.